Two-part collapsible corrugated paper form void

Abstract

A two-part collapsible form void for providing a space between a poured concrete structure and an underlying expansive soil is formed of a foldable outer section and a foldable inner section which, when erected, is longitudinally slidable into the erected outer section. The form void may be shipped in the separated and collapsed state, reducing shipping volume by up to 85 percent, and is easily erected by hand at the job site.

What is claimed is: 
     
       1. A two-part collapsible form void for establishing a space in or adjacent to a concrete structure, including: an outer part comprising, a first sheet of planar material folded over onto itself along a longitudinal fold line and forming first and second portions, wherein said first portion is defined by joined together coextensive strips along two adjacent sides to form a bottom flange, and wherein said second portion is defined by the remainder of the folded first sheet, said second portion having,   parallel longitudinal fold lines defining an upper panel, a coextensive base panel, a first side panel and a second side panel, and second strut panels attached to the middle sheet along first and second longitudinal fold lines, said strut panels, in the erected position of the void form, depending downwardly at an angle from the middle sheet, whereby said strut panels extend between the middle sheet and the said parallel longitudinal fold lines which define an intersection between the base panel and the first and second side panels.     
     
     
       2. The combination of claim 1 where the inner part comprises a plurality of contiguous sheets of planer material comprising first and second portions, wherein the first portion of the inner part is defined as the central transverse portion of each of said sheets and a second portion is defined as the remainder of said sheets, and further including, adhesive means joining the said sheets over the first portion thereof.   
     
     
       3. The two-part collapsible void form of claim 2 wherein said plurality of contiguous sheets comprise, a top sheet, having top and bottom surfaces, generally coextensive with said upper panel of said outer part,   a second sheet having an elongate central portion adhered to the bottom surface of the central transverse portion of the top sheet, and first the first side of said middle panel, and a second strut panel adjacent the second side of said middle panel;   erecting said outer part by unfolding said panels to form a rectangular parallelogram;   erecting said inner part by unfolding said panels relative to each other to form an articulated inner structure enclosable within said outer part; and   slidingly inserting said inner part into said outer part whereby said top panel extends generally between the fold lines defining said upper panel, and said strut panels extend generally to the fold lines defining said base panel.   
     
     
       4. The two-part collapsible form void of claim 3, further comprising an end cap substantially covering an end of said form void between said upper panel, base panel, and side panels. 
     
     
       5. The two-part collapsible form void of claim 4, wherein said end cap is adjoined to said top panel at a fold line and includes a fold-in tab which is insertable into said form void adjacent said base panel. 
     
     
       6. The two-part collapsible form void of claim 4, wherein said end cap is adjoined to said upper panel at a fold line and includes a fold-in tab which is insertable into said form void adjacent said base panel. 
     
     
       7. The two-part collapsible form void of claim 3, wherein said top sheet of the inner part is proximate the said upper panel upon insertion of the inner part into the outer part. 
     
     
       8. The two-part collapsible form void of claim 1, wherein the first sheet of planar material is corrugated paper having parallel corrugation ribs lying in a direction perpendicular to said parallel longitudinal fold lines of said outer part. 
     
     
       9. The two-part collapsible form void of claim 1, wherein said inner part is symmetrical about a vertical elongate central plane. 
     
     
       10. The two-part collapsible form void of claim 3, wherein said inner part further comprises: a first sheet comprising a top panel generally coextensive with said upper panel;   a second sheet of comprising: a middle panel joined to the central portion of said top panel;   a first strut panel on one side of said middle panel, said first strut panel folded downwardly to bear against the fold line between said base panel and said first side panel; and   a second strut panel on the opposite side of said middle panel, said second strut panel folded downwardly to bear against the fold line between said base panel and said second side panel.     
     
     
       11. The two-part collapsible form void of claim 1, wherein said inner part further comprises: a first sheet comprising: a top panel having a transverse center portion and disposed generally coextensive with and underlying said upper panel;   a first side support panel joined to one side of said top panel and configured to be folded downward to a vertical orientation generally coextensive with and adjacent to the first side panel when inserted into said outer part;   a second side support panel joined to an opposite side of said top panel and configured to be folded downward to a vertical orientation generally coextensive with and adjacent to the second side panel when inserted into said outer part;     a second sheet of corrugated paper comprising: a middle panel having first and second sides and joined to the transverse central portion of said top panel;   a first strut panel adjacent the first side of said middle panel, said first strut panel folded downwardly to bear against the fold line between said base panel and said first side panel; and   a second strut panel adjacent the second side of said middle panel, said second strut panel folded downwardly to bear against the fold line between said base panel and said second side panel.     
     
     
       12. The two-part collapsible form void of claim 11, further comprising a third sheet generally coextensive with said second sheet and joined coextensively thereto. 
     
     
       13. The two-part collapsible form void of claim 11, further comprising a third sheet generally coextensive with said second sheet and joined thereto. 
     
     
       14. A two-part collapsible form void for establishing a space in or adjacent to a concrete structure, comprising: an outer part formed of a first sheet of planar material wherein said first sheet is centrally folded longitudinally and coextensive longitudinal strips along two adjacent sides are joined by adhesive, said joined strips comprising a bottom flange, said first sheet provided with parallel longitudinal fold lines defining an upper panel, a coextensive base panel, a first side panel and a second side panels whereby said first sheet is erected to a rectangular parallelogram cross-section with said bottom flange extending outwardly from and coplanar with the base panel; and   an inner part slidably insertable into the erected outer part and formed of a plurality of sheets of planar material, said sheets comprising a plurality of panels formed by joining a transversely central portion of said sheets with adhesive and folding opposing portions of one sheet downwardly along longitudinal parallel fold lines adjacent said joined portion.   
     
     
       15. A method for fabricating a collapsible longitudinal form void from corrugated paper with corrugation ribs lying in a first direction, comprising: preparing an outer part comprising a first rectangular sheet of corrugated paper having first and second sides perpendicular to the first direction and centrally folded perpendicular to the first direction and being joined by adhesive along a thin strip at the first and second sides of said first sheet;   forming fold lines parallel to said central fold in said first sheet to define an upper panel, opposing side panels on each side of said upper panel, and a base panel joining said side panels;   preparing an inner part comprising: forming a top panel comprising a second rectangular sheet generally coextensive with said upper panel;   forming fold lines in a third rectangular sheet, having first and second parallel sides, to define a middle panel, a first strut panel adjacent whereby said first sheet is erected to a hollow form having a rectangular parallelogram cross-section with said bottom flange extending outwardly from and coplanar with the base panel, and   an inner part slidably insertable into the erected outer part and having,   at least one sheet of material having a planar transversely central portion and opposing angularly folded lateral strut panel portions defined by parallel fold lines on either side of the central portion.     
     
     
       16. The method of claim 15, wherein a portion of said inner part is inserted into one outer part, and a remainder of said inner part is inserted into another outer part to form a unitary form void of increased length.